Use of silicones to improve die-clicking of bonded nonwoven polyester fibrous sheets



p 3, 1963 e. L. HARRISON 3,400,013

IE-CLICKING OF BO USE OF SILICONES TO IMPROVE D NONWOVEN POLYESTER FIBROUS SHEETS Filed Jan. 22, 1965 NDED United States Patent 3,400,013 USE OF SILICONES TO IMPROVE DIE-CLICKING OF BONDED NONWOVEN POLYESTER FIBROUS SHEETS Gerald L. Harrison, Morrisville, Pa., assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware Filed Jan. 22, 1965, Ser. No. 427,249 4 Claims. (Cl. 117138.8)

ABSTRACT OF THE DISCLOSURE A process for treating nonwoven sheets of polyethylene terephthalate fibers bonded with a copolyester which comprises uniformly applying to such sheets from about 0.01 to 1% by weight of a liquid silicone having a viscosity of 50 to 10,000 centistokes at C., the silicone being in a volatile liquid vehicle, and heating the sheet in a quiescent atmosphere at a temperature above 120 C. but below the melting point of the copolyester for a period of between about 6 and 18 hours. This process improves processability of the sheet.

British Patent 932,482 published Nov. 20, 1963, describes a nonwoven sheet of continuous organic polymeric filaments in which the filaments are disposed in random configuration throughout the structure. One embodiment comprises a nonwoven fibrous sheet of 80% by weight polyethylene terephthalate fibers and 20% binder fibers of a polyester copolymer. It has been found that a particularly desirable sheet is obtained when the binder fibers are constituted by a copolyester derived from ethylene glycol, and a mixture of 79 mol percent terephthalic acid, and 21 mol percent isophthalicacid. The nonwoven sheet prepared from this blend of polyester fibers is heated to partially fuse the copolymer fibers and to bond the entire structure together. This embodiment is particularly desirable for use as stilfeners and linings in garments, particularly in collars or cuffs.

One of the commercial methods for fabricating garments requires preparation of identical parts by what is known in the trade as die-clicking. This operation is similar to the die-stamping of other industries. In the textile industry, for example in making mens shirts, certain parts such as collar liners or cuff liners are cut by die-clicking several layers of fabric at one time. It has been found that the above-mentioned nonwoven fiber sheets and others prepared from polyester fibers tend to stick or fuse together at the edges as a result of the dieclicking operation. The stacks of cut pieces are difiicult to separate, and considerable time and expense is therefore required to separate the cut pieces.

During manufacture and subsequent use, collars and cuffs are subjected to hot ironing. It is important that the lining material retain its original whiteness during these ironing operations; otherwise the color of the liner may actually show through the covering fabric. It is also important that the lining material not stick to or melt through the covering fabric. This is particularly important when the covering fabric is of lightweight construction such as is used in mens shirts or tailored womens blouses, or dresses.

An object of the present invention is to provide an improved polyester fiber sheet for use in die-clicking operations wherein the sheet will be made more resistant to sticking and still be substantially free from yellowing. Others will be apparent from the following disclosure.

Accordingly, the invention comprises uniformly applying to a fibrous sheet comprising polyethylene terephp Ce thalate fibers bonded by a copolyester from 0.01 to 1% by weight of a liquid silicone having a viscosity of 50 to 10,000 centistokes at 25 C., and heating the sheet in a substantially quiescent atmosphere at a temperature above 120 C. and below the melting point of the said copolyester for between about 6 and 18 hours.

In a preferred embodiment of the invention the sheet is rolled up on a mandrel after silicone application and is heated in an unventilated chamber for the required period. FIGURE 1 is a diagram showing the treatment of a polyester fiber sheet by passing it through a pair of nip rolls to coat the sheet with a silicone dispersion or solution.

FIGURE 2 is a partial cross section of a die-clicking apparatus showing a multilayer stack of sheet material after cutting.

FIGURE 3 is a garment part prepared by die-clicking.

FIGURE 4 is a cross-sectional view of an unventilated chamber used to heat-treat the silicone-treated fabric on a mandrel.

Considering now FIGURE 1, a bonded nonwoven polyester fiber sheet 1 is pulled from supply roll 2, and passed across idler roll 30: to the nip of a pair of rolls 4a and 4b, one of which picks up a silicone dispersion from bath 5. The bath contains a mixture of liquid silicone in a liquid vehicle. A very small quantity of the bath liquid is coated on the fibrous sheet during passage between rolls 4a and 4b. Straight-edged blade 6 removes excess liquid from roll 4b. The siliconecoated fabric 7 passes over idler roll 3b and is wound-up on removable mandrel 8. The roll of fabric 7 is removed from the coating machine on mandrel 8 when a substantial amount of sheet mate-rial has been wound upon it. It is transferred to an oven 9 shown in FIGURE 4 wherein the entire roll of sheet material is heated in a substantially quiescent atmosphere. The oven has an opening 10 for equalizing pressure with the outside air but no provision for the introduction and circulation of fresh air. The mandrel rests on supports 11. The roll of siliconecoated fabric is removed from the oven after heating for 6 to 18 hours.

The treated fabric is then wound off the roll and folded, pleated, or cut and stacked to form a multilayer stack of nonwoven fibrous sheet material. Any common fabric handling techniques may be used for this operation. The multilayer stack is then die-clicked as shown in FIGURE 2. The multilayer stack 23 is placed upon platform 24. The die is actuated by a stamping machine not shown through connection 22. A die 20 having sharp cutting edges 21 is used to stamp outthe fabric pieces 26 having the same shape as the die cutting edges 21. The die passes vertically through the sheet finally stopping on platform 24, and is thereafter withdrawn.

In the coating operation it is preferable to use a liquid silicone having a viscosity of 50 to 10,000 centistokes at 25 C. and to apply 0.01 to 1.0% by weight based on the weight of the fabric, preferably less than 0.10% to the fabric. In general, larger amounts tend to give the fabric an undesirable slippery quality. This tendency is less noticeable when a poly-dirnethylsiloxane is used.

A uniform coating of silicone is suitably applied to the nonwoven sheet by use of a direct gravure coating roll. This type of coater enables one to uniformly apply very small quantities. The lower roll has a finely engraved surface. For uniformity of application, silicone is ordinarily applied from a bath containing a mixture of up to 10% by weight liquid silicone and at least by weight of a volatile liquid vehicle. The liquid vehicle may be removed by evaporation or may be allowed to remain on the fabric.

The volatile liquid vehicle may be water or an organic liquid. The vehicle may either be a true solvent or a h V cone. The damp fabric was wound up on a roll. The

dispersant. Preferably it should be a crystallizing agent for polyesters. Application of the silicone by means of a waterdispersion or from other liquid low molecular weight crystallizing agents is desirable for this reason. About 1% water concomitantly coated on the fabric with the 0.01 to 1.0% silicone gives improved results. The fabric may be heat treated or an entire roll of the fabric may be heat treated batchwise on a mandrel in the oven as shown in FIGURE 4. The latter process is particularly effective because it provides a longer exposure period in the oven, without excessive cost. The resulting material is more crystalline than the material originally provided.

The silicone lubricants are semi-organic polymers that moleeularly contain an inorganic backbone of repeating silicon-oxygen units and organic side groups which are attached to the silicon atoms in the polymer chain. The general structure of the silicone fluids is as follows:

l \t /.l

In the above formula R represents alkyl or aryl groups such as methyl or phenyl, which may be the same throughout the compound or may diifer, and It indicates the number of recurring units of the type shown in parenthesis. The liquid silicones are relatively short polymers as compared to silicone rubbers and have little or no crosslinking as compared to silicone resins. For the present invention only the silicone liquids are satisfactory, the rubbers and resins being too viscous or insoluble to apply in the small concentration needed for the present invention. Methyl substituents are preferred for the present invention.

The preparation and use of silicones is described in Synthetic Lubricants, a book edited by R. C. Gunderson and A. W. Hart, Rheinhold Publishing Corp., New York, 1962. The relation between viscosity and molecular weight is shown on p. 272, Table 7.1.

EXAMPLE 1 A fibrous polyester nonwoven sheet 18 inches in width was prepared by the method of the British patent mentioned above. The sheet material was composed of 87% polyethylene terephthalate fibers and 13% copolymer polyester fibers. The copolymer was derived from ethylene glycol and a mixture 79 -mol percent terephthalic acid and 21 mol percent isophthalic acid, i.e., polyethylene terephthalate/isophthalate 79/21. The homopolymer and copolymer fibers were randomly laid on a moving belt to obtain a sheet Weighing about 2 oz./yd. The collected sheet material was bonded by heating to partially melt the copolymer fibers without melting the homopolymer. A roll of the bonded polyester fibrous nonwoven sheet was treated by continuously passing the sheet material through a direct gravure coater as shown in FIGURE 1. The lower engraved roll 4b rotated in a bath 5 comprising a dispersion of 6% silicone, 94% water, and a small amount of surface-active agent. Excess liquid was removed from the roll by blade 6.

The silicone used in the dispersion had a viscosity of 350 centistokes at C. being primarily a polydimethylsiloxane having three methyl substitutions on the end silicon atoms. The sheet material, which was continuously removed from the gravure coater, contained about 1.25% by weightwater and 08% by weight siliroll of sheet material was transferred to an unventilated oven and heated batehwise for 12 hours at C. After heat treatment the dry sheet contained 0.08% silicone uniformly distributed over the area of' the sheet. The sticking temperature of the sheet increased at least 10 C. Stick temperature is defined as the lowest press temperature at which the nonwoven polyester sheet material sticks to either of two enclosing layers of shirting material.

A multilayer stack of the sheet was made by folding the sheet in zig-zag fashion with creases every 18 inches along its length. The resulting stack containing 30 layers of nonwoven sheet material. The stack was placed under the die in a stamping machine to prepare fabric parts to be used as stiffener for shirt collars. The material was stamped with a die having the shape of the desired fabric part. Sufiicient pressure was applied to pass through all layers of the fabric. The materials were completely separable and there was no sticking from layer to layer. The fabric pieces had a shape similar to that shown in FIGURE 3. In the FIGURE 3, fibers 31 are randomly disposed. The border 30 of the cut fabric had the shape r of the die cutting edge 21 of FIGURE 2 and all of the fabric pieces had the same shape and total area.

A shirt collar was made by sandwiching the die-cut piece of fibrous polyester nonwoven sheet between two layers of cotton shirting material. The resulting laminate did not melt or turn yellow when ironed at a temperature of C. and the nonwoven polyester sheet material did not stick to the woven shirting material.

While the above description illustrates the preparation of shirt collars, it is obvious the method may be applied in part or in total to the preparation of other garment parts (pockets, sleeve cuffs, belt linings, etc.) and for other uses such as shoe linings or shoe doublers.

What is claimed is:

1. A process for treating nonwoven sheets of polyethylene terephthalate fibers bonded with a copolyester which comprises uniformly applying to such sheets from about 0.01 to 1% by weight of a liquid silicone having a viscosity of 50 to 10,000 centistokes at 25 C., the silicone being in a volatile liquid vehicle, and heating the sheet in a quiescent atmosphere at a temperature above 120 C. but below the melting point of the copolyester for a period of between about 6 and 18 hours.

2. The process of claim 1 wherein the liquid silicone is polydimethylsiloxane.

3. The process of claim 1 wherein the volatile liquid vehicle is water.

4. The process of claim 1 wherein the copolyester comprises polyethylene terephthalate/isophthalate.

References Cited UNITED STATES PATENTS 2,676,128 4/1954 Piccard ..11714 0X 2,839,158 6/1958 Reinauer 117140X FOREIGN PATENTS 932,482 7/1963 Great Britain.

WILLIAM D. MARTIN, Primary Examiner.

5 T. G. DAVIS, Assistant Examiner. 

